1. Technical Field
The present invention relates to ball joints and, more particularly, to a hybrid ball stud for a ball joint comprised of a bolt and a spherical polymeric component secured to the head of the bolt to define a ball segment of the ball stud.
2. Discussion
As is known, motor vehicles are equipped with suspension systems for absorbing road shock and other vibrations while providing a smooth and comfortable ride for the vehicle occupants. In virtually all vehicular suspension systems, ball joints are used to interconnect suspension components for accommodating changes in angularity therebetween. In general, most conventional ball joints include a ball stud, a ball socket, and a housing. Typically, the ball stud is a forged metallic component having an elongated shank segment and a ball segment. The shank segment of the ball stud is connected to one suspension component and the housing is fixed to the other suspension component. The ball segment of the ball stud is retained in a spherical cavity formed in the ball socket which, in turn, is mounted in the housing. To facilitate angular movement of the ball stud relative to the housing, the sphericity and surface profiles of the ball segment must be highly precise. These component characteristics have conventionally required the utilization of expensive and time-consuming secondary machining and finishing operations.
As an alternative to forged ball studs, it is known to provide a ball joint equipped with a ball stud having a polymeric layer molded over the ball segment. See, for instance, U.S. Pat. Nos. 2,862,740, 2,905,492 and 3,091,486. As a further alternative, some ball studs have a polymeric ball mounted to one end of a threaded stud. See, for example, U.S. Pat. Nos. 2,999,709, 3,023,038, 3,941,495 and 5,697,142. Finally, it is also known to surround a portion of a threaded stud with a partially spherical polymeric insert and which engages a radial flange extending from the stud. See, for example, U.S. Pat. No. 2,823,055, 2,846,252, 2,937,895, 2,953,401, 3,091,486, 4,334,795 and 4,629,352. In each case, a molded component is used as the ball segment to limit or eliminate the secondary surface finishing operations associated with conventional forged ball studs.
Although various composite assemblies have been proposed for constructing a ball stud to avoid the machining and heat treating requirements associated with forged ball studs, none have been successful in significantly reducing production costs. Therefore, it would be desirable to provide a ball joint having a composite ball stud requiring minimal labor and processing costs.
The present invention provides a ball joint for use in interconnecting a pair of components to accommodate relative angular movement therebetween. The ball joint includes a socket assembly and a hybrid ball stud. The socket assembly includes a cup-shaped housing defining a cavity therein and an insert disposed within the housing cavity and which defines a spherical ball socket. The hybrid ball stud includes a standard bolt and a polymeric insert attached to, or encapsulating, the head of the bolt to define a spherical ball or a partial spherical ball. The polymeric insert is adapted to be retained in the ball socket. The bolt is a high-volume commercially-available component having a threaded shank segment and a head segment which is over-molded or fitted with the polymeric insert. As such, an inexpensive hybrid ball stud is provided for use in ball joints.
As a further feature of the present invention, a partially spherical polymeric member may be molded on, or attached to, the shank segment of the bolt such that the polymeric member and the spherical head segment of the bolt combine to serve as the ball segment of the ball stud.
According to another feature of the present invention, a toroidal polymeric member is molded on, or attached to, the head of the bolt to serve as the ball segment of the ball stud.